The present invention is directed to a non-arcing electrical switch. More particularly, the present invention pertains to an auxiliary lighting circuit for use with a gaseous discharge lamp.
An auxiliary lighting circuit generally refers to a circuit which activates a lamp, usually incandescent, when the primary lighting means is interrupted or fails. Auxiliary lighting circuits are widely used on gaseous discharge lamps to provide light in the event the gaseous discharge lamp fails or is interrupted.
Due to their high efficiency and long life span, gaseous discharge lamps are commonly used in retail displays, gymnasiums, factories, hallways, outdoor sports lighting, streets, parking areas, and bridge underpasses. Commonly known examples of gaseous discharge lamps include fluorescent and High Intensity Discharge (HID) lamps, such as metal halide, sodium, and mercury vapor lamps.
Light can be produced in these discharge lamps by establishing an arc through a gas, a process known as electric discharge, or gaseous discharge. However, it can take several seconds for the arc to be established, and several minutes until full light output is reached. If power to the gaseous discharge lamp is interrupted, the discharge lamp must be allowed to cool for a time, usually several minutes, before the arc can be reestablished and normal operation resumed.
To compensate for the lack of light during the period of time when the discharge lamp is not illuminated or is in a low luminescence condition, a standby, or auxiliary, incandescent lamp is typically connected to the discharge lamp to provide auxiliary lighting. The auxiliary lighting circuitry senses the state of the discharge lamp and energizes the secondary/auxiliary lamp. When power is applied, the auxiliary lamp illuminates while the discharge lamp has time to cool then restrike/relight, at which time the auxiliary lamp is extinguished. A time delay feature keeps the auxiliary lamp on during the discharge lamp's warm up period prior to automatically turning off the auxiliary lamp. The auxiliary lamp typically operates from a 120 VAC supply.
Previous auxiliary lighting circuits, however, are severely limited in their range of application. Typically, they are designed to measure specific voltage levels to determine the status of the discharge lamp. Also, the previously known auxiliary discharge lamps have no general applicability to other lamps aside from the gaseous discharge lamp to which it is connected. Furthermore, known auxiliary lighting circuits that are capable of detecting current rather than voltage may need levels of load current to be relatively high in order to detect it. In addition, the repeatability, reliability, and speed of reset timers in known auxiliary lighting circuits are a concern.
Accordingly, there is a need for an improved auxiliary lighting circuit for use with a lamp, particularly with a gaseous discharge lamp. Desirably, such an auxiliary lighting circuit can detect lower load currents than formerly was possible with known auxiliary lighting circuits, has reduced reset times during power interruptions, and has improved reset reliability and repeatability. In addition, it is desirable to have an auxiliary lighting circuit that maintains the auxiliary lamp voltage at 120 V, regardless of input voltage and can operate a timing circuit at 2 V or less.